One afternoon last fall, Armand Neukermans, a tall engineer with a sweep of silver bangs, flipped on a noisy pump in the back corner of a Sunnyvale lab. Within moments, a fine mist emerged from a tiny nozzle, a haze of salt water under high pressure and heat.

It didn't look like much. But this seemingly simple vapor carries a lot of hope - and inspires a lot of fear. If Neukermans' team of researchers can fine-tune the mechanism to spray just the right size and quantity of salt particles into the sky, scientists might be able to make coastal clouds more reflective.

The hope is that by doing so, humankind could send more heat and light back into space, wielding clouds as shields against climate change.

The fear, at least the one cited most often, is that altering the atmosphere this way could also unleash dangerous side effects.

"Ten years ago, people would have said this is totally wacky," Neukermans said. "But it could give us some time if global warming really becomes catastrophic."

It's now beyond debate that the globe is getting hotter. The ice caps are melting, sea levels are rising, and extreme weather events like droughts, floods and hurricanes are increasing.

Even if public policymakers manage to significantly curtail future fossil-fuel emissions - the carbon dioxide and other greenhouse gases that the vast majority of climate scientists blame for climate change - the hundreds of gigatons we've already pumped into the atmosphere have probably locked in a series of life-altering consequences.

Neukermans and his colleagues are among an unofficial cadre of Bay Area scientists, technologists, designers and engineers who have begun the hard work of preparing for a warmer world. They're exploring unconventional concepts that might help us live with the consequences - or prevent them from spinning out of control.

It's not clear yet if any will work, or find the support to move off the drawing board. All are sure to be costly and controversial.

But much is at stake. Rising temperatures and sea levels threaten the region's homes, habitat, industries and infrastructure (see related story).

Balancing risk, reward

The concept of "cloud brightening" dates back 22 years, when British physicist John Latham first proposed it in a little-noticed paper in the journal Nature.

But as the threat of global warming rises, it and other "geoengineering" strategies have shifted from the scientific fringes into mainstream debate. Geoengineering is a broad category for techniques that could remove greenhouse gases from the atmosphere or reflect away more heat, including things as innocuous as painting roofs white and as controversial as spraying sulfate particles into the stratosphere.

The basic idea behind cloud brightening is to equip ships with mechanisms like the ones Neukermans' team is designing and aim them at the relatively low-lying clouds that hug the western coasts of continents. It would probably require hundreds - if not thousands - of vessels (see related story).

Few are eager to tweak a system as complicated, sensitive and interconnected as the climate. But many scientists worry that nations simply won't cut fossil-fuel emissions enough to prevent rising temperatures from unleashing humanitarian and ecological calamities.

"If we have to intervene, we should be doing the research now, because these ideas are extremely complicated and extremely risky," said Jane Long, a former associate director at Lawrence Livermore National Laboratory. "I hope we never have to do it, but I think it's irresponsible not to understand as much as we possibly can in case we need it."

Critics, however, argue that scientists are talking about tinkering with a system they don't fully understand. Altering the clouds could affect rainfall patterns, with potentially devastating consequences, they say.

"Large and small, these things all have other environmental effects and they're not solving the problem," said Kert Davies, research director at environmental group Greenpeace. He believes research efforts and dollars should be focused instead on clean-energy technology.

"Geoengineering is like taking an aspirin for pain without addressing the disease," he said.

A pro bono project

Neukermans, a 72-year-old serial inventor from Belgium, agrees that the best response to climate change is to curtail greenhouse emissions.

Cloud brightening is "absolutely no replacement for the other things we should do," he said. "We should cut CO2 as much and as fast as we can."

But that's simply not happening, even as predictions for rising temperatures this century soar past 2 degrees Celsius, the threshold that most climate scientists point to as the clear danger zone. So Neukermans and his team feel compelled to move ahead with their work.

Neukermans arrived in the United States in 1964. Over a four-decade career at General Electric, Hewlett-Packard, Xerox and elsewhere, he put his name on more than 75 patents. In 1997, he founded Xros, an optical switch company that pulled off the holy grail of telecom at the time: using tiny mirrors to move data through fiber network switches without converting them from pulses of light into electrical signals. In 2000, Nortel Networks acquired the company for $3.25 billion in stock.

Since retiring, Neukermans has dedicated his time and money to a series of social and environmental causes, including efforts to develop land-mine-detection technology and inexpensive prostheses for the poor.

He turned his attention to cloud brightening in early 2010, recruiting a team made up mostly of former colleagues, after the Bill Gates-supported Fund for Innovative Climate and Energy Research provided money for an initial viability test.

As the group attempts to develop an actual prototype, Neukermans is covering the expenses out of his own pocket - and the group is working pro bono.

The five-man team is an esteemed contingent of Silicon Valley's old guard. Most are in their 60s or 70s; they have playfully referred to themselves as the "Silver Linings."

But they're engineering heavyweights, boasting 250 years of experience and 130 patents among them. They include Lee Galbraith, inventor of a breakthrough tool for inspecting semiconductors, and Jack Foster, a laser pioneer who helped create the first checkout scanners.

Moving toward trials

It's clear that cloud brightening is possible. Satellites have observed "ship tracks," or whitened lines in marine clouds that large vessels have formed inadvertently by pumping out particles in their exhaust. Unknown is whether humans can do it purposely, on a large enough scale to matter, and without severely altering weather patterns elsewhere.

Scientists at the Met Office Hadley Centre in England ran computer simulations of wide-scale cloud brightening and saw sharp rainfall decreases in South America, with disastrous impacts on the Amazon rain forest.

Caldeira ran his own models for all ocean clouds and found that rainfall would decline over sea, but increase over land. More recently, physicist Latham, now at the National Center for Atmospheric Research in Boulder, Colo., put the Met Office's models to work and found the potential impact on the Amazon could be minimized by altering the location and amount of cloud brightening.

The conflicting results underscore some uncertainty about the overall consequences, in part because of the complexity of modeling the behavior of clouds. So as researchers get closer to working mechanisms for cloud brightening, it raises a critical question: What standards should apply before anyone tests such technology in the real world?

Last September, Latham and other scientists called for limited field trials once a nozzle technology is developed.

They were careful to stress that tests must be carefully planned to prevent any damage to the ecosystem, and said they should be conducted in an "open and objective manner" with consultations between international scientific organization and potential stakeholders.

Questions, concerns

But is preventing any fallout from such testing an achievable goal? And is it possible for all affected parties to reach consensus on these issues?

Wil Burns is dubious.

The director of the energy policy and climate program at Johns Hopkins University terms himself an "extreme skeptic" of cloud brightening. Even if it works, he's not convinced scientists will be able to easily identify or deal with any unintended consequences.

There's also the touchy question of social equity. Cloud brightening might cool global temperatures on average, but what if it leads to deforestation in South America or affects monsoon patterns in Asia? If the world is better off on average - particularly in the relatively temperate first world - is it acceptable that some nations suffer?

Such issues aside, Burns worries that politicians, energy companies and consumers will fail to perceive these tools the way scientists hope they will: as an option of last resort. Rather, he fears, they'll see them as an excuse to continue dumping waste into the atmosphere.

And even if geoengineering initially works, researchers might run into some disastrous side effect that only becomes clear over time, forcing them to cut off those efforts after a few years or decades.

"If you stopped, you'd get a massive carbon pulse and temperature increases as much as 10 to 30 times greater than if you'd continued climate change policy as it is," Burns said. "It would just be catastrophic."

Caldeira argues that the distant consequences of limited cloud brightening are likely to be minimal, and stresses that any effects would trail off within weeks of shutting it down. But he too believes it might be premature for real-world tests. Acting too precipitously could sow further skepticism, limiting long-term options, Caldeira said.

"To me it seems prudent to hold back on doing field experiments, mostly because I'm afraid of backlashes," he said.

At a minimum, any limited field tests should be conducted by entities like the National Science Foundation, and include rigorous review processes and government participation, Long and other scientists stress.

Thinking long-term

Caldeira suggests that the world might have to literally feel the heat - perhaps witnessing mass starvation or the migration of millions of climate refugees - before geoengineering becomes politically palatable.

By then, though, it could be harder to conduct research in a deliberative, dispassionate manner. That's why some want to move ahead sooner rather than later.

"We'd just like to examine the ideas we're involved with," Latham said. "And ideally, if they work, just pop them on the shelf."

Despite some reports to the contrary, Neukermans and his colleagues emphatically deny that they intend to test the technology on actual clouds. If they manage to build working prototypes, they plan to turn them over to academic or government researchers. They're content to leave the deployment as well as the debate to others, and just do what engineers do: solve the tricky technical puzzle before them.

But there is another force driving Neukermans, a father of four and grandfather of eight. In his eighth decade, after a lifetime of inventions, he would like to use his talents to devise one more - one that would really count.

"The next generation is a consideration for all of us," he said. "I hope we never have to use this, but if we do, we'd make a contribution on a scale you could never envision."

About the series

Inside cutting-edge Bay Area research aimed at containing climate change.